Collector intended to be used in deinking of waste paper according to the flotation process

ABSTRACT

A collector that is intended to be used at deinking of waste paper according to the flotation process. The collector includes a polyester obtained through reaction between polyalkylene glycol, di and/or tricarboxylic acid and/or anhydrides thereof as well as a saturated fatty acid with 12-18 carbon atoms. The polyester shows a molecular weight between 3000-10000.

BACKGROUND OF THE INVENTION

Around the world the opinion for use of the recycled fibre is nowgrowing. A number of countries have already legislated that a certainpart of the total paper production shall be constituted of recycledfibre. The methods, which are used today at deinking are the flotationprocess and the washing process, where the later is mainly applied inNorth America. The flotation process, which is most common in Europe,technically originates from the mining industry and is the process beingmost interesting for our object.

The deinking can be divided in three different steps; 1) dissolution ofrecycled fibre and discharging printing-ink from the fibres, 2)dispersing printing-ink in the water phase and 3) separation of theprinting-ink. These three steps are included in both flotation processand the washing process. The method, which one uses industrial dependson the requirements and conditions which are found where the activity islocated. The object of the flotation process concerning the deinking isto remove the very most amount of printing-ink from a recycled fibresuspension. The first step is to solve the fibre and disengage theprinting-ink. When this is accomplished the particles must be modifiedso that they obtain suitable physical and chemical characteristics sothat they afterwards can be lifted to the surface and removed with helpof air-bubbles.

Some parameters are important to be consider at the flotation, such asthe size of the particle, airflow in the flotation cell, the size of theair-bubbles, temperature, flotation time, the concentration of therecycled fibres in the flotation cell, pH, the concentration of thechemicals as well as the degree of the hardness of the water.

The flotation process is carried out in such a manner that the recycledraw material of the fibre is poured out through mechanical treatment incombination with a concentration of the chemicals. Different methodsconcerning chemicals/the concentration of the chemicals and method topour the raw material exist. The purpose of the mechanical treatment isthat the fibres should be rubbed against each other and that one in thatway, together with the chemicals, should get an efficient discharging ofprint-ink. However, a too strong mechanical influence causes greatdamages on the fibres and this is not desirable at the paper-making.

Then comes filtering, whereby the particle shaped impurities areseparated, followed of a purification step, generally by means of avortex cleaner, where very little and heavy particles are separated. Ina dispersing step the discharge of printing-ink continues throughmechanical treatment and chemical influence. Printing-ink and remainingsmall particles are separated subsequently in the flotation step.Different flotation technics exist and in the more contemporary ones,one can float all small particles by pressurizing the flotation cell.Small impurities are separated through washing and to increase thebrightness of the pulp the bleaching is performed through hydrogenperoxide or hydro sulphite.

Following chemicals are used at the deinking:

Sodium hydroxide. (NaOH)

Sodium hydroxide is used to adjust pH to the alkaline level and tosaponificate and/or hydrolyse the resin in the printing-ink. The pH at,which the deinking occurs, 9.5-11.0, causes that the fibres swell andthereby become more flexible, Adding NaOH to the mechanical pulps makesthe pulp to turn yellow and become dark. The concentration of NaOH mustbe optimized. The alkalinity must be high enough, as mentioned earlier,to obtain good saponification and hydrolysis of resins, which areincluded in the printing-inks. A sufficient high pH also gives a goodfibre flexibility as well as an optimal function of the hydrogenperoxide. A quandary, as mentioned earlier, is that in the volumes withhigh lignin content the high alkali content give rise to chromophoregroups. These chromophore groups are the reason for the pulp becomingyellow dyed. Experiments done show that the brightness increases withincreasing pH when it is increased from 8.6 to 10.2, subsequently thebrightness diminishes. Increasing number of magazine paper in the pulprequires additional content of sodium hydroxide. Before the pulp is usedfor paper making pH is reduced to about 5.5. It is shown that thebrightness increases linear with decreasing pH between 8.5 and 5.5. Thereason for the brightness increase is not determined entirely but onesupposes that it depends on two main factors: agglomeration of thecolloidal printing-ink as well as reduction of the number ofchromophors.

Hydrogen peroxide. (H₂ O₂)

Hydrogen peroxide is used to discolour the chromophors, which areoriginate from alkaline pH in the pulp. The peroxide reacts with thesodium hydroxide according to the following:

    H.sub.2 O.sub.2 +NaOH→HOO-+Na.sup.+ +H.sub.2 O

when pH=10.0-11.5 and temperature=40°-80° C.

The perhydroxyl anion (H00-) is the active bleach chemical. Theconcentration of this, is influenced by the following parameters: pH,temperature, dose of hydrogen peroxide and the concentration of thecertain metal ions such as Fe, Mn, Cu and others. The influence of themetal ions can be reduced by adding chelate and sodium silicate. Certainmicroorganisms can also have negative influence by producing peroxidedegrading enzymes.

Sodium silicate

Sodium silicate, or water-glass, is a flotation silicate, which consistsof SiO₂ and Na₂ O in varying mole ratio. Sodium metal silicate has amole ratio (Na₂ O/SiO₂) of approximately one and is the one mainly beingused within the deinking. This is due to the higher alkalinity of thesilicates with the low mole ratio. Actually, the Silicate component is amixture of many complex polymer silicate anions. By forming colloidswith heavy metal ions the sodium silicate prevents a degradation of thehydrogen peroxide. The silicate even prevents the loose printing-inkfrom reprecipitating on the fibres. The silicate has also a bufferingeffect on pH. Up to a certain level the brightness of the pulp increaseswith added concentration of the sodium silicate. However, theconcentration of the silicate should be kept as low as possible, sinceproblems with the deinkings in the subsequent equipment have been noted.

Chemicals forming agglomerate

The printing-ink from the office waste form thin flake at the deinking.These are to big to be able to be removed by flotation or washing and tolittle to be able to be removed through filtration. If a chemical thatchanges the surface structure of the platform is added, they can be madeto form agglomerate, which can be removed, e.g. through centrifugation.

The surface-active substances

The group of surface-active substances include many subgroups. Forinstance dispersing substances, collectors, substances with wettingcharacteristics, substances that prevents redeposition and so on, can bementioned. As a matter of principle, the surface-active substances beingused for deinking will have two important components. A portion of themolecule must be hydrophillic and the other one must be of hydrophobicquality. The structure of the surface-active substances can be astraight chain, branched chain, they can have charged groups, long orshort chain, double or simple bindings and so on.

Complex builder

DTPA (diethylentriaminpentaacetic acid) is the most used complex builderbut EDTA (ethylendiamintetraacetic acid) is also used. The complexbuilders act by building solvable complexes of heavy metal ions. Thecomplex prevents these ions from breaking down the hydrogen peroxide.DTPA, which has a structure with five "legs" is a more efficient complexbuilder than EDTA, which has a structure with four "legs".

Today, the waste paper manufacturers largely use a raw material mixture,which normally 30-40% consists of magazine paper and to 60-70% ofnewspaper. It is possible by sorting magazine paper and newspaper by areasonably cost-effective method. By knowing, which print methods andprinting-inks being used, we can easily understand, which mechanisms andfunctions that are required in the deinking works. For further operationone must also consider following facts about the printing-inks andprinting methods:

Pigment consists of very fine carbon particles.

The carriers consist of mineral or vegetable oils or as well asdissolver, which evaporates.

The printing-ink at printing on newspapers is partly absorbed by thepaper and thereby contains oils, which make the colour to not drycompletely. The printing-ink on the magazine paper consists of enduredpigment on the paper surface, which largely consists of filler. Thiscauses that a smaller amount of colour be adsorbed on the cellulosefibre.

Both foregoing types of printing-inks have a pronounced hydrophobicquality.

Earlier, the chemical system at flotation has been described to give aninsight into what effect the different added ingredients have on thedeinking. When the collector is added, the printing-ink is dispersed inthe water phase. Now it is required to modify the particles so that theyobtain characteristics, which makes it easy for them to be flotated.

If one makes the small hydrophillic particles more hydrophobic, thisgives a certain agglomeration. This yields heavier particles with ahydrophobic surface structure. An important condition for the particleto come in contact with the air-bubble is that the particle has anappropriate size.

If the particle is to light, it will follow the flow round the bubbleand no effect is obtained. If the particle is to heavy a collision withthe air-bubble is obtained, however, the adhesive powers are too weak inproportion to its pulp. Therefore, the particle falls off and theflotation effect does not occur. It is therefore very important that theparticle is sufficiently big. Earlier experiments have shown that anoptimal size for the particle is about 100 μm.

The hydrophobic surface structure favours an adsorption to air-bubbles.The adsorption can be explained using surface chemistry, whereby throughan interface between the air and the water the hydrophobic matters areoriented against the air phase. This occurs because it is advantageousfrom an energy point of view. To be able to achieve a hydrophobing ofthe particles, one can add a surface-active chemical.

The conventional type of flotation chemical has required a high degreeof hardness of the water to obtain intended effect. This acquiresproblem with depositions in form of CaCO₃ in the equipment. For a periodthere has been different alternatives to the original flotationchemicals, for instance so-called synthetic collector, which do notrequire a high water hardness.

In SE-B-464 639 a synthetic collector, which consists of a polyesterbased on a polylalkylene glycol and a di or tricarboxylic acid isdescribed. Tall oil is used of the polymerization reaction to controlthe chain length of the resulting polymer. The collector produced inthis manner is efficient and also non-polluting, as it is biologicallydegradable. However, there is still place for enhancements, for examplethe possibility of controlling the polymerization reaction and the chainlength of the polyester.

THE OBJECT AND THE MOST IMPORTANT CHARACTERISTICS

The object of the invention is to obtain an efficient syntheticcollector, where the polymerization reaction can be controlled in abetter way to thereby increase the reproducibility and give a morewell-defined product. Naturally, the environmental aspects applying thebiological degradability should be satisfied.

This, according to the invention has been achieved by including apolyester obtained through reaction between 1) polylalkylene glycol, 2)di- and/or tricarboxylic acid and/- or anhydrides thereof as well as 3)a saturated fatty acid with 12-18 carbon atoms, and, which polyestershows a molecular weight between 3000-10000.

DESCRIPTION OF THE DRAWINGS

FIG. 1 is a block diagram showing the brightness increase at flotationexperiment with a collector according to the invention by differentdosages.

FIG. 2 is a block diagram showing the brightness increase at flotationexperiment with a collector according to the invention and a commercialcollector.

DESCRIPTION OF THE INVENTION

The collector is a polyester made of a polylalkylene glycol and a diand/or tricarboxylic acid or its anhydrides. Preferably, aspolylalkylene glycol polyethylene glycol, PEG, HO--(CH₂ --CH₂ O)_(n) --Hand/or polypropylene glycol, PPG, HO--(CH₂ --CH₂ --CH₂ 0)_(n) --H areused. These can occur in several different molecular weights. We haveused PEG as average molecular weight 400.

Preferably, as di or tricarboxylic acid is used maleic acid, fumaricacid, adipic acid, citric acid, oxalic acid or sebacic acid or itsanhydrides. Mixtures can also be used.

To obtain a certain chain length a blockage acid at the synthesis isadded and in the experiments, already described tall oil (Bevacid-20),myristic acid, lauric acid and stearic acid has been used. Through thepolycondensation between PEG and maleine acid a chain with a relativehydrophillic structure caused by carboxyl groups and oxygen atoms isobtained. It is also desired a strong hydrophobic part on the moleculeand this characteristic is obtained by choosing a hydrophobic blockageacid. When one varies the polymerisation ratio and the length of theblockage acid, different efficiency with the collector is obtained.

Tall oil consists of 25-30% resin acids and 70-75% fatty acids. Theportion of fatty acid in the tall oil is approximately 5% saturated,approximately 25% consists of oil acid and approximately 70% consists oflinolenic acid. The mixture of different fatty acids makes it difficultto decide the appearance of the collector, but if estimation is done onecan establish that the half the tall oil consists of linolenic acid.

According to the invention three saturated fatty acids with 18, 14 and12 carbon atoms respectively, i.e. stearic acid, myristic acid andlauric acid have been tested as blockage acids. To be able to study howthe chain length of the molecules affected the collector function,synthesis with calculated molecular weights (Mn) of 3000, 5000 and 7000were made. The average molecular weight should be between 3000-10000.

A polyester was formed by gradually polymerization between two bi ormultifunctional monomers. By a bifunctional monomer is meant a moleculewith two functional groups. The reaction is also called condensationpolymerization because the water is separated.

EXAMPLE xHO--R--OH+xHOCO--R--COOH≈HO --R--OCO--R--COO--!_(x) H+(2x-1)H₂O

Generally, condensation polymers are formed through graduallyintermolecular condensation of reactive groups. Condensation polymerscan also be formed through additional polymerisation. Bifunctionalmonomers give linear polymers, while polyfunctional gives branched orcross linked polymers. To interrupt the reaction one usually uses amonofunctional acid, which is called blockage acid.

To obtain a linear polymeric with high molecular weight the exchangemust be much higher. A ratio of a transformer of 90%, for instance givesonly one average of 10 repeating units in the chain. High exchange isobtained for instance by means of displacing the equilibrium in theabove reaction to right. It is also important that the monomers areadded in equimolar quantities and there are no impurities present. Thetemperature should not be too high, since there is a risk of bireaction,which leads to cross-linkage and branching. To obtain a fasterpolymerization one usually adds a strong acid as catalyst, for instancesulphuric acid or p-toluensulphonic acid. It is also possible to usecertain tin organic combinations as catalysts.

The prerequisite for gradually polymerization is following:

any of the two present reactants can react.

the concentration of the monomer decreases fats in the beginning of thereaction.

the molecular weight of the polymer increases whole the time during thereaction.

long reaction time is necessary to obtain high molecular weight.

Synthesis of the collector

The included raw materials were poured in a flange flask, the heatingwas started and the catalyst added. Timekeeping was started when thecatalyst was added. Nitrogen was conducted in the mixture to obtain acertain stirring as well as to prevent oxygen supply. To improve thestirring a magnetic agitator was used. Water suction was used since lowpressure lowers both partial pressures of water vapour in the flask andthe boiling point at the reaction mixture.

To be able to obtain a controlled temperature increase as well as beable to carry out the synthesis at a constant temperature an adjustabletransformer was connected to the heat casing. The synthesis went on inabout three hours. Sometimes the synthesis was interrupted earlierbecause the mixture became too viscous or a certain acid ratio wasobtained. At regular intervals samples for control of the acid ratiowere taken.

The synthesis was accomplished at 150°, 175° and 200° C. respectively tobe able to study the impact of the synthesis temperature on themolecular weight. For each synthesis a double sample is performed tocontrol the reproducibility for the synthesis. After each synthesis theamount of the given water was measured and this condensate wascontrolled by means of FTIR. The synthesis product was characterized bymeans of FTIR (Fourier Transform Infrared Spectroscopy), acid ratio,viscosity and in a certain case even by means of NMR (Nuclear MagneticResonance), clouding point and PLC (High Pressure LiquidChromatography).

When a surface-active substance is present as a diluted water solution,during the clouding point, the molecules are dissolved well. If thetemperature is increased, the molecules begin to approach each othermore and more. Finally it is visible when the solution becomes milky.This is called the clouding point. Because of this it is important thatthe molecule is designed with regard to the flotation temperature. Anumber of different collectors were produced according to followingrecipe and reaction conditions:

    ______________________________________                                        COLLECTOR 1, 2, 4                                                                          COLLECTOR 3, 5                                                                              COLLECTOR 6, 7                                     ______________________________________                                        Reaction time:                                                                             Reaction time:                                                                              Reaction time:                                     240, 210, 210 min resp.                                                                    165 and 150 min resp.                                                                       180 and 150 min                                    150° C.                                                                             175° C. otherwise                                                                    200° C. otherwise                           Maleic acid                                                                           102 g    as 1, 2       as 1, 2                                        PEG 400 461 g                                                                 Tall oil                                                                               35 g                                                                 ______________________________________                                        COLLECTOR 8, 9                                                                             COLLECTOR 10, 11                                                                            COLLECTOR 12, 13                                   ______________________________________                                        Reaction time:                                                                             Reaction time:                                                                              Reaction time:                                     210 and 195 min rasp.                                                                      155 and 180 min rasp.                                                                       188 and 180 min                                    150° C.                                                                             175° C. otherwise                                                                    200° C. otherwise                           Madein acid                                                                           116 g    as 8, 9       as 8, 9                                        PEG 400 400 g                                                                 Tall oil                                                                               40 g                                                                 ______________________________________                                        COLLECTOR 14 COLLECTOR 15, 17                                                                            COLLECTOR 16                                       ______________________________________                                        Reaction time:                                                                             Reaction time:                                                                              Reaction time:                                     180 min.     180 min.      150 min.                                           175° C.                                                                             150° C. otherwise                                                                    200° C. otherwise                           Maleic acid                                                                           102 g    as 14         as 14                                          PEG 400 461 g                                                                 Stearic acid                                                                           40 g                                                                 ______________________________________                                        COLLECTOR 18 COLLECTOR 19  COLLECTOR 20                                       ______________________________________                                        Reaction time:                                                                             Reaction time:                                                                              Reaction time:                                     210 min.     180 min.      210 min.                                           150° C.                                                                             150° C.                                                                              150° C.                                     Maleic acid                                                                           116 g    Maleine acid                                                                            116 g Maleine acid                                                                          116 g                                PEG 400 400 g    PEG 400   400 g PEG 400 400 g                                Tall oil                                                                              103 g    Stearic acid                                                                            108 g Tall oil                                                                               57 g                                ______________________________________                                        COLLECTOR 21 COLLECTOR 22  COLLECTOR 23                                       ______________________________________                                        Reaction time:                                                                             Reaction time:                                                                              Reaction time:                                     180 min.     180 min.      180 min.                                           150° C.                                                                             150° C.                                                                              150° C.                                     Maleic acid                                                                           116 g    Maleine acid                                                                            116 g Maleine acid                                                                          116 g                                PEG 400 400 g    PEG 400   400 g PEG 400 400 g                                Stearic acid                                                                           60 g    Myristic acid                                                                            34 g Lauric acid                                                                            30 g                                ______________________________________                                        COLLECTOR 24 COLLECTOR 25  COLLECTOR 26                                       ______________________________________                                        Reaction time:                                                                             Reaction time:                                                                              Reaction time:                                     180 min.     240 min.      150 min.                                           150° C.                                                                             150° C.                                                                              200° C.                                     Maleic acid                                                                           116 g    Fumaric acid                                                                            116 g Fumaric acid                                                                          102 g                                PEG 400 400 g    PEG 400   400 g PEG 400 461 g                                Lauric acid                                                                            76 g    Myristic acid                                                                            34 g Stearic acid                                                                           40 g                                ______________________________________                                        COLLECTOR 27                                                                  ______________________________________                                        Reaction time:                                                                115 min.                                                                      150° C.                                                                Fumaric acid                                                                          116 g                                                                 PEG 400 400 g                                                                 Stearic acid                                                                           40 g                                                                 ______________________________________                                    

In all synthesis other than 1 and 6, 1 ml concentrated sulphuric acidsolved in 2 ml water was used as catalyst. In synthesis 1 no catalystwas used and in synthesis 6 methane sulphone acid was used.

In table 1 below synthesis data is shown.

                  TABLE 1                                                         ______________________________________                                                                              CATALYST,                                               SYN-                  TEOR.MW                                                 THESIS                g/mole,                                 COL-   Blockage TEMP.   Acid VISCOSITY,                                                                             synth. time,                            LECTOR acid     °C.                                                                            ratio                                                                              mpas.23° C.                                                                     Min.                                    ______________________________________                                        1      Tall oil 150     49.5 653      no, --, 240                             2      --       --      15.5 3210     yes, --, 210                            3      --       175     8.1  5380     yes, --, 165                            4      --       150     7.8  2640     yes, --, 210                            5      --       175     9.5  4960     yes, --, 150                            6      --       200     11.3 2100     yes, --, 180                            7      --       --      7.7  >10000   yes, --, 150                            8      --       150     15.1 >10000   yes, 7000, 210                          9      --       --      22.8 8720     yes, 7000, 195                          10     --       175     12.5 >10000   yes, 7000, 155                          11     --       --      16.4 >10000   yes, 7000, 180                          12     --       200     12.4 >10000   yes, 7000, 180                          13     --       --      12.8 >10000   yes, 7000, 180                          14     C-18     175     4.7  >10000   yes, --, 180                            15     --       150     7.6  >10000   yes, --, 180                            16     --       200     3.1  >10000   yes, --, 150                            17     --       150     6.1  >10000   yes, --, 180                            18     Tall oil --      38.2 3710     yes, 3000, 210                          19     C-18     --      33.0 >10000   yes, 3000, 180                          20     Tall oil --      27.3 6830     yes, 5000, 210                          21     C-18     --      32.3 >10000   yes, 5000, 180                          22     C-14     --      22.4 >10000   yes, 7000, 180                          23     C-12     --      31.5 >10000   yes, 7000, 180                          24     --       --      33.1 >10000   yes, 3000, 180                          25     C-14     150     25.3 >10000   yes, 7000, 240                          26     C-18     200     5.4  >10000   yes, --, 150                            27     C-18     150     58   >10000   yes, 7000, 115                          ______________________________________                                         C-18 in the table signifies technical stearic acid                            C14 signifies myristic acid                                                   C12 signifies lauric acid                                                

Polymer calculations

The amount of the included reactant was calculated through followingmethod:

The average polymerisation ratio, X_(n), which is the number ofbifunctional molecules at the beginning of the reaction divided by thetotal number of polymer molecules, is calculated according to following:

    X.sub.n =(1+r)/(1+r-2xrxp)                                 (1)

but also according to

    X.sub.n ═M.sub.n /m                                    (2)

where

M_(n) =the average molecular weight

m=the molecular weight for the repeating unit in the molecule

r=N_(A) /N_(B) <1

p=ratio of transformation

If p is set to 1, then it is obtained:

    X.sub.n =(1+r)/(1-r)→r=(X.sub.n -1)(X.sub.n +1)     (3)

The amount of blockage acid is calculated according to following:

    r=(N.sub.A)/(N.sub.A +2N.sub.B)

By stoic measurement balance N_(A) =N_(B) and thereby becomes:

    N.sub.B =(N.sub.B --N.sub.B xr)/r                          (4)

where N_(A) and N_(B) is the number of bifunctional molecules and N_(B)is the number of monofunctional molecules, i.e. the blockage acid.

To calculate the number of blockage acid the desired molecular weightwas firstly decided. Subsequently X_(n) according to (2) was calculated.By means of (3) and (4) the number of blockage acid could be calculatedlater.

Acid ratio determination

Approximately 2 g sample was weighed in a 300 ml E-flask. 100 ml ethanolwas poured in a 300 ml E-flask and 15-20 drops phenolphthalein solution(0.05%) was added. The ethanol was titrated with 0.1M KOH until lightrose alteration (only some drops) and was added to the saturated test.Agitation was applied until the test was solved. The test solution wastitrated until rose-coloured alternation and amount of required ml KOHwas read off. The titration must be performed fast, since CO₂ from airis solved in the solution and uses KOH.

Calculation

Acid ratio=M×k×V/m=56.1×0.1×V/m=5.61×V/m

M=mole weight of potassiumhydroxide (56.1)

k=concentration of the KOH-solution

V=number of ml KOH consumed by the titration

m=weighted amount of sample in g

Flotation experiment with the collector

Daily and magazine newspapers were torn to pieces in approximately 4×4cm pieces. After control of the dryness the newspapers and water as wellas chemicals were collected in a pulper vessel. After slushing the pulpslurry is allowed to rest after, which pH was controlled. Subsequentlythe slurry was further grinded with an Ultra-Turrax to obtain a morecomplete fibre release. The pulp was poured in the flotation cell andwater was added. If the collector was not added in connection with theinitial slushing we added it before the flotation. The flotation wasstarted. During the above mentioned steps we held a slurry temperatureof 40° or 45° C., depending on flotations receipt. pH was measured afterthe slushing. Sample for manufacturing brightness sheet and control ofwhite water purity (see below) was taken before and after the flotation.Also, the sample was taken of the foam from the scrape.

At the tests 150 g paper raw material in 70% newspaper and 30% magazinepaper, 2.5 l water (40° C.), 3.2 g water-glass (46.8%)-1% dosage of dryrich pulp, 1.5 g NaOH-1% dosage, 0.45 g surfactant-0.3% dosage (wasreduced later to 0.075 g, i.e. 0.05% dosage) were used. The mixturediluted to 5% pulp concentration and slushed in a pulper for 5 min. Itswelled subsequently in 1 h after, which slushing occurred for 5 min. pHwas measured until the mixture was diluted to 10 litre and stirred.

The slurry was poured in the flotation cell, which was filled with 40°C. water. 1 litre was taken out for production of the brightness sheetand control of the white water purity. The flotation chemicals wereadded in form of 0.75 g collector-0.5% dosage. At flotation with soapbased collector 0.3 g-0.2% dosage was added. Also, 1.78 g CaCl₂ wasadded to obtain 7° dH.

The flotation was accomplished in 30 min. After the flotation, 10 litreswere tapped from the cell and the sample was taken for brightness sheetand the water phase.

Brightness sheet

Brightness sheet was made according to SCAN standard C11:75. 1 litresample was taken out from the flotation cell and poured in mixer so thatthe fibres were separated from each other. The mixture diluted to 2litre and pH adjusted to 4.0-5.5. 4samples of 0.5 litres were sucked outin Buchner funnel with the diameter of 11 cm. The sheet was pressed orrolled and dried in room temperature. The brightness was decidedsubsequently.

White water purity

The white water was controlled by following method: 200 ml suspensionwas taken out from the cell and fibres were filtered by a net basket. 60ml of the filtrate was filtered through Munchtell filter paper type 00A(diameter=5.5 cm). After drying was measured the brightness.

In table 2 the acid ratio as well as the brightness increase(Δ-brightness) for the different collectors are indicated.

                  TABLE 2                                                         ______________________________________                                                     Δ-brightness (ISO R457)                                    COLLECTOR      White water                                                                             Brightness sheet                                     ______________________________________                                         1             --        2.11                                                  2             --        2.12                                                  2             2.97      3.40                                                  3             --        2.85                                                  4             3.17      2.48                                                  4             3.30      3.61                                                  5             6.49      1.97                                                  6             4.33      3.90                                                  6             3.17      3.65                                                  7             0.44      3.09                                                  7             3.46      3.17                                                  8             2.38      3.63                                                  8             3.74      2.85                                                  9             4.24      3.66                                                 10             7.77      4.70                                                 10             3.84      4.32                                                 11             5.56      3.89                                                 0-sample       2.64      3.71                                                 0-sample       1.52      0.73                                                 Soap (0.2%)    5.57      5.14                                                 Soap (0.2%)    4.02      1.34                                                 Tenneco (0.5%) 4.40      2.32                                                 Tenneco (0.5%) 2.05      1.90                                                 Bimex 400 (0.5%)                                                                             3.74      4.11                                                 ______________________________________                                    

Result

Totally, 27 collectors were manufactured. By the attempts carried out,it was reviled that a collector based on polyethylene glycol, maleicacid and stearic acid gave the best result. The molecular weight for thecollector has been determine to approximately 6500 through HPLC. Theclouding point was 57° C. The composition of the products and averagemolecular weight was controlled by means of NMR, FTIR and HPLC.

The viscosity measurements point out that the molecular weight increaseswith the synthetic temperature. Possibly a certain cross linking athigher temperature. Small differences in acid ratio but greatdifferences in viscosity between the collector made at differentsynthetic temperatures indicates this.

The clouding point of the collector should be in few degrees above theflotation temperature. We recommend that a number of differentcollectors are produced or optimal performance when the flotationtemperature varies between different deinking plants.

It has not been able to indicate any connections between the flotationeffect and the acid ratio. We have been able to discern better flotationresult for products with higher viscosities. By comparisons between thedifferent blockage acids the stearic acid has given best flotationresult. Tall oil as blockage acid has given uneven flotation result,which perhaps can be explained through its any complicated composition.

For the best collector, no 16, we optimized the dosage. Experiment withincreasing concentration show that 0.3% concentration collector gavebest result. Higher amount gave poor flotation result. The results areshown in FIG. 1. Comparing the experiment with a calcium stearate basedcommercial collector, Tenneco®, and the collector 16 according to theinvention showed that, to attain same Δ-brightness, 4.5 units(ISO-R457), on brightness sheet as for a concentration of 0.35%collector 16, a concentration of 1.2% of Tenneco® was demanded, i.e. 3.5times higher dosage. These results are shown in FIG. 2.

We claim:
 1. A composition for deinking waste paper according to theflotation process, the composition comprisinga polyester obtainedthrough reaction of (1) a polyalkylene glycol, (2) a dicarboxylic acid,a tricarboxylic acid, an anhydride of a dicarboxylic acid, an anhydrideof a tricarboxylic acid, and combinations thereof, and (3) a saturatedfatty acid having from about 12 to about 18 carbon atoms, the polyesterhaving a molecular weight of from about 3,000 to about 10,000 daltons.2. The composition according to claim 1, wherein the polyalkyleneglycol, dicarboxylic acid, tricarboxylic acid, anhydride of adicarboxylic acid and anhydride of a tricarboxylic acid are aliphaticcompounds.
 3. The composition according to claim 2, wherein thepolyalkylene glycol is selected from the group consisting ofpolyethylene glycol, polypropylene glycol and combinations thereof.
 4. Amethod for using a polyester as a collector for deinking waste paperaccording to the flotation process, comprising:obtaining a polyesterhaving a molecular weight of from about 3,000 to about 10,000 daltons,the polyester being produced by a reaction between 1) a polyalkyleneglycol, 2) a di and/or tricarboxylic acid and/or anhydrides thereof, and3) a saturated fatty acid having from about 12 to about 18 carbon atoms;and using the polyester as a collector for deinking waste paperaccording to the flotation process.
 5. The composition according toclaim 1 wherein the dicarboxylic acid is selected from the groupconsisting of maleic acid, fumaric acid, adipic acid, oxalic acid,sebacic acid, and combinations thereof.
 6. A composition for deinkingwaste paper according to the flotation process, the compositioncomprising a polyester obtained through reaction of a polyalkyleneglycol, citric acid, and a saturated fatty acid having from about 12 toabout 18 carbon atoms, the polyester having a molecular weight of fromabout 3,000 to about 10,000 daltons.
 7. The composition according toclaim 1 wherein the polyester has a molecular weight of from about 5,000to about 10,000 mass units.
 8. A composition for deinking waster paperaccording to the flotation process, the composition comprising apolyester obtained through reaction of 1) a polyalkylene glycol, 2) adicarboxylic acid, a tricarboxylic acid, an anhydride of a dicarboxylicacid, an anhydride of a tricarboxylic acid, and combinations thereof,and 3) a saturated fatty acid selected from the group consisting ofstearic acid, myristic acid, lauric acid, and combinations thereof, thepolyester having a molecular weight of from about 3,000 to about 10,000daltons.
 9. The composition according to claim 1 wherein thepolyalkylene glycol is polyethylene glycol, the dicarboxylic acid ismaleic acid, and the saturated fatty acid is stearic acid.
 10. Acollector for deinking waste paper, the collector being produced by theprocess comprising:forming a mixture comprising, prior to reaction, (1)a polyalkylene glycol, (2) a dicarboxylic acid, a tricarboxylic acid, ananhydride of a dicarboxylic acid, an anhydride of a tricarboxylic acid,and combinations thereof, and (3) a saturated fatty acid having fromabout 12 to about 18 carbon atoms; and heating the mixture at atemperature and for a sufficient period of time to form a collectorhaving a molecular weight of from about 3,000 to about 10,000 daltons.11. A polyester ink collector produced by reaction of maleic acid, PEG400 and stearic acid.